Production of ethanol from starch-containing material is well-known in the art. The production of ethanol as a bio-fuel has become a major industry, with in excess of 21 billion gallons of ethanol being produced worldwide in 2012.
The most commonly industrially used commercial process, often referred to as a “conventional process”, includes liquefying gelatinized starch at high temperature (around 85° C.) using typically a bacterial alpha-amylase, followed by simultaneous saccharification and fermentation carried out anaerobically in the presence of a glucoamylase and a Saccharomyces cerevisae yeast.
Yeast which are used for production of ethanol for use as fuel, such as in the corn ethanol industry, require several characteristics to ensure cost effective production of the ethanol. These characteristics include ethanol tolerance, low by-product yield, rapid fermentation, and the ability to limit the amount of residual sugars remaining in the ferment. Such characteristics have a marked effect on the viability of the industrial process.
Yeast of the genus Saccharomyces exhibit many of the characteristics required for production of ethanol. In particular, strains of Saccharomyces cerevisiae are widely used for the production of ethanol in the fuel ethanol industry. Strains of Saccharomyces cerevisiae that are widely used in the fuel ethanol industry have the ability to produce high yields of ethanol under fermentation conditions found in, for example, the fermentation of corn mash. An example of such a strain is the yeast used in commercially available ethanol yeast product called Ethanol Red™.
Strains of Saccharomyces cerevisiae are used in the fuel ethanol industry to ferment sugars such as glucose, fructose, sucrose and maltose to produce ethanol via the glycolytic pathway. These sugars are obtained from sources such as corn and other grains, sugar juice, molasses, grape juice, fruit juices, and starchy root vegetables and may include the breakdown of cellulosic material into glucose.
Although strains of Saccharomyces cerevisiae currently used in the fuel ethanol industry are well suited to ethanol production, there is an increasing need for improvements in the efficiency of ethanol production owing to the increased demand for ethanol as a fuel, and the increased availability of starch in new strains of corn.
There is therefore a need for new strains of Saccharomyces capable of improving the efficiency of ethanol production in industrial scale fermentation. There is also a need for new strains of Saccharomyces that reduce the acetaldehyde level after fermentation compared to current commercial strains, such as ETHANOL RED™.
Further, despite significant improvement of ethanol production processes over the past decade there is still a desire and need for providing processes of producing ethanol from starch-containing material that can provide a higher ethanol yield.